1. Field of the Invention
The present invention relates to a method, an apparatus, and a program for processing tomographic images, that generate optical tomographic images using OCT (Optical Coherence Tomography).
2. Description of the Related Art
Conventionally, optical tomographs that utilize OCT measurement are employed to obtain tomographic images of living tissue. In an optical tomograph, a low coherence light beam emitted from a light source is divided into a measuring light beam and a reference light beam. Thereafter, a reflected light beam, which is the measuring light beam reflected by a measurement target when the measuring light beam is irradiated onto the measurement target, is combined with the reference light beam. Tomographic images are obtained, based on the intensity of a interference light beam obtained by combining the reflected light beam and the reference light beam. There are some optical tomographs that utilize TD-OCT (Time Domain Optical Coherence Tomography) measurement. In TD-OCT measurement, the measuring position in the depth direction (hereinafter, referred to as “depth position”) within a measurement target is changed, by changing the optical path length of the reference light beam.
Recently, OCT apparatuses that generate optical tomographic images at high speeds without changing the optical path length of the reference light beam, by utilizing FD-OCT (Fourier Domain Optical Coherence Tomography) measurement, have been proposed. SD-OCT (Spectral Domain Optical Coherence Tomography) measurement and SS-OCT (Swept Source Optical Coherence Tomography) measurement are two types of FD-OCT measurement (refer to Japanese Unexamined Patent Publication No. 2006-189424, and Y. Yasuno et al., “Three-dimensional and high-speed swept-source optical coherence tomography for in vivo investigation of human anterior eye segments”, OPTICS EXPRESS, Vol. 13, No. 26, pp. 10652-10664, 2005). In SD-OCT measurement, low coherence light beam having a predetermined wavelength band is divided into a measuring light beam and a reference light beam by a Michelson interferometer, to obtain tomographic images. In SS-OCT measurement, the frequency of a laser beam emitted from a light source is swept. Reflected light beams of each wavelength are caused to interfere with the reference light beam. The intensities of reflected light beams at a depth positions within a measurement target are obtained by administering Fourier analysis on interference spectra for the series of wavelengths. The tomographic images are obtained employing the detected intensities.
In the aforementioned OCT measurement, the measuring light beams are irradiated on the measurement targets while being scanned. The tomographic images are generated, by arranging tomographic data obtained in the depth direction of the measurement targets (the direction of the optical axis of the measuring light beams) in the scanning directions.
The tomographic images obtained by the aforementioned OCT measurement have different properties in the scanning directions and the optical axis directions of the measuring light beams. Accordingly, when processes to improve the image quality of the tomographic images are administered, there is a problem that desired image quality improvements cannot be obtained, if uniform image processing conditions are applied in both the scanning directions and the optical axis directions of the measuring light beam.